Activation of the Basal Plane in Two Dimensional Transition Metal Chalcogenide Nanostructures

Han, Jae Hyo,Kim, Hong Ki,Baek, Bongkwan,Han, Jeonghee,Ahn, Hyun S.,Baik, Mu-Hyun,Cheon, Jinwoo American Chemical Society 2018 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.140 No.42

<P>Achieving a molecular level understanding of chemical reactions on the surface of solid-state nanomaterials is important, but challenging. For example, the fully saturated basal plane is believed to be practically inert and its surface chemistry has been poorly explored, while two-dimensional (2D) layered transition-metal chalcogenides (TMCs) display unique reactivities due to their unusual anisotropic nature, where the edges consisting of unsaturated metals and chalcogens are sites for key chemical reactions. Herein, we report the use of Lewis acids/bases to elucidate the chemical reactivity of the basal plane in 2D layered TMCs. Electrophilic addition by Lewis acids (i.e., AlCl<SUB>3</SUB>) selectively onto sulfides in the basal plane followed by transmetalation and subsequent etching affords nanopores where such chemical activations are initiated and propagated from the localized positions of the basal plane. This new method of surface modification is generally applicable not only to various chemical compositions of TMCs, but also in crystal geometries such as 1T and 2H. Nanoporous NbS<SUB>2</SUB> obtained by this method was found to have an enhanced electrochemical energy storage capacity, offering this chemical strategy to obtain functional 2D layered nanostructures.</P> [FIG OMISSION]</BR>

Antioxidant Content and Properties of Commonly Consumed Dried Vegetables in Korea

Jinwoo Yang, Jeehye Sung, Hyeonmi Ham, Hyemin Han, and Junsoo Lee 忠北大學校 農業科學硏究所 2015 農業科學硏究 Vol.31 No.1

This study evaluated the antioxidant content and activity of fourteen different indigenous Korean vegetables, as well as the relationship between antioxidant content and activity. DPPH and ABTS radical scavenging activities, through their inhibitory effect on lipid peroxidation, as well as their reducing power, have been used to investigate the antioxidant activity of 14 vegetables extracts. Polyphenolic and flavonoid concentrations were measured using spectrophotometric methods. Ascorbic acid analysis was carried out using HPLC. The polyphenolic, flavonoid and ascorbic acid concentrations were measure to be 0.24-11.34, 0.0079-10.84 and 0-71.35 mg·100 g-1, respectively. The extracts of Aster scaber Thunb, Capsicum annuum L. leaves, Cirsium setidens, and Morus alba leaves demonstrated significantly high level of antioxidant activity and higher antioxidant content. In addition, these vegetables demonstrated significant positive correlations between antioxidant activity and polyphenolic and flavonoid content. However, no relationship was found between antioxidant activity and ascorbic acid. Therefore, polyphenolic and flavonoid compounds are major antioxidants in vegetables. Our results could have a direct impact on vegetable consumption by increasing consumer awareness of the health benefits of vegetables.

Measurement of magnetization loss according to the winding pitch of CORC®

Jinwoo Han,Kyeongdal Choi,Woo-Seok Kim,Ji-Kwang Lee 한국초전도저온공학회 2021 초전도와 저온공학 Vol.23 No.4

For the application of HTS wire to AC power equipment, a conductor with high current capacity and low loss is required. CORC® , one of the high-current conductors manufactured using several HTS wires, is made by winding the wires in a spiral on a cylindrical former. Because the magnetization loss of a CORC® conductor depends on the degree of magnetic coupling between the wires constituting the CORC® , it is necessary to know the value of the magnetization loss of the CORC® itself. In order to obtain an accurate loss value, it is necessary to know the effect of the ratio of the winding pitch of the CORC® conductor in the pickup coil region sampling the magnetization loss signal. To confirm this effect, we prepare CORC® samples having various winding pitches, and measure and compare the magnetization losses. In addition, the magnetization loss was measured while rotating the CORC® samples and it was examined whether there was a difference in the magnetization loss according to the rotation.

Morphological Studies of Polymer Dispersed Liquid Crystal Materials

Jinwoo Han 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.2I

In this work, we have studied the morphologies of polymer dispersed liquid crystals (PDLCs) based on E7/NOA61. Scanning electron microscope studies show that the PDLC morphology is strongly affected by the LC concentration and the cure temperature. A typical PDLC morphology with isolated LC droplets dispersed in a polymer matrix is only observed at low LC compositions and at low cure temperatures. Increasing either the LC composition or the cure temperature results in a polymer ball morphology, in which LCs exist in irregularly shaped voids in the polymer network structure. It is shown that the transition between these two morphologies can be qualitatively explained using a pseudo-binary phase diagram.20

Estimation of the critical current of CORC® conductor using the measured magnetization losses

Jinwoo Han,Ji-Kwang Lee,Kyeongdal Choi,Woo-Seok Kim 한국초전도저온학회 (구 한국초전도저온공학회) 2022 한국초전도저온공학회논문지 Vol.24 No.4

Measurement of magnetization loss according to the winding pitch of CORC®

Jinwoo Han,Kyeongdal Choi,Woo-Seok Kim,Ji-Kwang Lee 한국초전도저온학회 2021 한국초전도저온공학회논문지 Vol.23 No.4

For the application of HTS wire to AC power equipment, a conductor with high current capacity and low loss is required. CORC®,one of the high-current conductors manufactured using several HTS wires, is made by winding the wires in a spiral on a cylindricalformer. Because the magnetization loss of a CORC®conductor depends on the degree of magnetic coupling between the wiresconstituting the CORC®, it is necessary to know the value of the magnetization loss of the CORC®itself. In order to obtain anaccurate loss value, it is necessary to know the effect of the ratio of the winding pitch of the CORC®conductor in the pickup coilregion sampling the magnetization loss signal. To confirm this effect, we prepare CORC®samples having various winding pitches,and measure and compare the magnetization losses. In addition, the magnetization loss was measured while rotating the CORC®samples and it was examined whether there was a difference in the magnetization loss according to the rotation.

Study of Memory Effects in Polymer Dispersed Liquid Crystal Films

Jinwoo Han 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.4

In this work, we have studied the memory effects in polymer dispersed liquid crystal films. We found that optical responses, such as the memory effects, of the films depended strongly on the morphology. For example, memory effects were observed for films with polymer ball morphologies; however, only weak hysteresis effects were observed for films with droplet morphologies. In particular, a stronger memory effect was observed for films with more complicated polymer ball structures. Coincidentally, TTE, the temperature at which the memory state is thermally erased, was generally higher for the films exhibiting a stronger memory effect. In addition, studies of the temporal evolution of the films show that the memory effects become stronger after films have been kept on the shelf for a period of time. This change is likely to be associated with a modification of surface anchoring properties at the LC-polymer interface.

TSTC 도체의 자화손실 계산

한진우(Jinwoo Han),김우석(Woo-Seok Kim),최경달(Kyeongdal Choi),이지광(Ji-Kwang Lee) 대한전기학회 2022 대한전기학회 학술대회 논문집 Vol.2022 No.7

유전 알고리즘 기반 레이더 펄스 모호성 해결방법

한진우(Jinwoo Han),조제일(Jeil Jo),김산해(Sanhae Kim),박진태(Jintae Park),송규하(Kyuha Song) 대한전자공학회 2015 전자공학회논문지 Vol.52 No.4

TDOA(Time Difference of Arrival) 기반 수동형 전자감시장비는 이격 동작하는 다수의 수신기에서 수신되는 전자파 신호의 펄스도착시간인 TOA(Time of Arrival) 정보를 이용하여 신호원의 공간상 위치를 탐지한다. 수신기 간 이격 거리 대비 신호원에서 방사되는 신호의 PRI(Pulse Repetition Interval)가 크지 않을 경우 TDOA 기반 위치탐지를 위한 각 수신기에서의 동일 펄스쌍 선정에 모호성이 발생될 수 있다. 본 논문에서는 이격 동작하는 각 수신기에서 수신한 펄스들과 신호원간의 순시 방향탐지결과인 AOA(Angle of Arrival)를 이용하여 펄스 선택의 모호성을 신호원의 위치와 신호원으로부터 수신한 펄스들과의 TDOA 최적화 문제로 변경하고 이를 유전 알고리즘 기반으로 TDOA 기반 위치탐지 과정에서 발생될 수 있는 동일 펄스 선택 모호성을 최소화할 수 있는 새로운 기법을 제안하며, 다양한 모의실험을 통해 제안된 기법의 성능을 분석하였다. Passive Surveillance System based on the TDOA detects the emitter position in the air using TOA of pulses comprising emitter signal from multiple receivers. In case that PRI of pulses from the emitter is not enough big in comparison with the distance among receivers, it causes the ambiguity problem in selecting proper pulse pairs for TDOA emitter geolocation. In this paper, a novel ambiguity resolution method of radar pulses is presented by using genetic algorithm after changing ambiguity problem into optimization problem between TDOA of received pulses from each receiver and emitter position. Simulation results are presented to show the performance of the proposed method.

SVM 기반 레이더 펄스 PRI 변조형태 인식방법

한진우(Jinwoo Han),진종현(Jonghyun Jin) 대한전자공학회 2017 대한전자공학회 학술대회 Vol.2017 No.6

The time intervals between the adjacent pulses of collected pulse trains from radar emitters have a specific patterns to detect its own signals and to hide the information of the pulses to enemy. ES system should analyze inter pulse characteristics such as pulse repetition interval to identify the emitter’s type and source. In this paper, we propose a novel method of recognizing PRI modulation type based on Support Vector Machine. The method is shown via computer simulation using Weka to be reliable and robust even in the presence of many spurious pulses.